We moved to our 3rd district in TN and they are stating she can't have her personal iPad with her TD Snap app but must use a school issued iPad. IEP from previous district lists her iPad as her speech generating device. In description they specifically mention my daughter "brings her own communication device to school, however the school has a backup device if needed." New school wants to replace personal iPad with school issued iPad after my nonverbal daughter was "caught" taking screenshots of the sentences she created in her own AAC device. ( My daughter is 12 and also has intellectual disabilities and will be further devasted if she can't have her own iPad.) 

Do I need to ask the school to provide a PWN for this? 

Yes, requesting a PWN is always a good idea.  But it doesn't always solve the problem.  Have you requested an IEP meeting with the new school district IEP team?  I would do that and discuss the change in the IEP, how it would affect your daughter, and how she wasn't doing anything wrong to have it taken away from her.  If you have it, I would bring data (provider recommendations, examples of meltdowns if her own iPad is taken away, etc.) showing why insisting on a school-issued iPad would create a barrier to her education.  Stick to data and her legal rights.  If still unresolved after the meeting, definitely request a PWN with a detailed explanation of why your request was denied.